<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			/* 利用 display:table-cell */
			.parent {
				width: 500px;
				height: 500px;
				border: 1px solid #000;
				display: table-cell;
				vertical-align: middle;
				text-align: center;
			}

			.child {
				width: 100px;
				height: 100px;
				border: 1px solid #999;
				display: inline-block;
			}
		</style>
	</head>
	<body>
		<div class="parent">
			<div class="child"></div>
		</div>
	</body>
</html>
